Electric lamp



, hlg W. w. ROBERTS ET All,

ELECTRIC LAMP Filed March lO. 1924 (CJ num/Lto@ Wllmmw Rbwh.

p atented Nw., n, aan.

'WILLIAM WODDR'UFF ROBERTS AND LYNN T. RBEBTS, 0F SBY'VTLLE, KENTUCKY.

MECTRIC Ll?.

applicati@ mea March 1o, 1924.. serial No. 698,138.

To all 'whom t may concern.

Be it known that we, .WILLIAM W. Ron- Entrs and LYNN T. ROBERTS,citizens of the United States, residing at Shelbyville, in the county ofShelby and State of Kentucky, have invented certain new and usefulImprovements in Electric Lamps, of which the following is aspecification.

- This invention relates to electricA lamps of the type employing a bulband filament such as are commonly known as incandesj cent lamps. l

The invention also relates to light-projectors Where such lamps areemployed.

In the employment cf light projectors such as the head lights on'automobiles. Tt is the direct intense rays from the filament which tendto cause such intense illumination as to produce glare with itsaccompanying dangers. Attempts fhave been made to over come this byproviding a screen between the filament and the eye of a personobserving the lamp. Such attempts have revolved themselves into twoclasses; in one of which the outer or front end of the lamp is frosted,made from opalescent glass or in some other manner made translucidinstead of transparent. In the other methods, an opaque screen has beenemployed. By the use of the first method much light is wasted,

being absorbed by the construction of the lamp employed and in thesecond method not only' is light wasted 'but a shadow is thrown by theopaque screen.

One important object of the present invention is to provide,v animproved construction of lamp of this type especially adapted for use inconnection with automobile headlights and the like and which is of suchnature as to eliminate direct observation of the filament while at thesame time utilizing as much of the light 'as could be utilized with anordinary clear glass lamp and without a screen.

A second important object ofthe invention is to provide an yimprovedlamp of this character wherein the injurious' effects of shadow will beeliminated. y

A third important object of the invention is to provide an improvedcombination of parabolic reliector with the improved lamp in such mannerthat certain of the rays from the filament will, after doublereflection, be p iojected in a straight parallel beam or penci beprojected to intersect each other and then Other rays, after singlereflection, will' spread in a cone, while still other ra s, withoutreflection, will spread out to iluminate the sides of the road.

With the above and other objects in view as will be hereinafterapparent, the invention consists in general of certain novel details ofvconstruction and combinations of parts hereinafter fully described,illustrated in the accompanying drawings and specically claimed.

In the accompanying `drawings like characters of reference indicate likeparts in the several views, and:

Figure 1 is a transverse section through 70 a headlight showing theimproved lamp in position and indicating by dotted lines the course ofthe light rays.

Figure 2 is a greatly enlarged side elevation, partly in section,through the improved lamp showing itsV construction.

In the present disclosure the lamp is shown as having an ordinary ovalbulb l0 provided with the usual metallic neck 11. This bulb also has theusual filament 12 disposed cen- 80 trally of the greatest transversediameter of the lamp. The bulb is made of the usual clear glass but onthe exterior of its outer or forward end it is provided with a coatingthe filament and bulb at the greatest diam\ 90 eter of the latter. lt ispreferred that the silver coating cover about one-sixth of the surfaceof the bulb, though it may cover somewhat more than this.

lfVith this construction the silver coating acts as a reflector andconstitutes a concave mirror confronting the filament 12. When such alamp as this Ais placed in the usual manner in a headlight 15' providedwith a parabolic reflector 16 and is soarranged that 100 the mirror 13is in alinement with and in Ifront of the focus of the reflector 16, andthe filament l2 also in front of the reflector focus, then, under thesecircumstances, cer

tain light rays as 17 emanating from the 105 filament 12 will strike themirror 13, be reected through the reflector focus to the re- Hector 16and there be ra second time reflected to pass forwardly in substantiallyparallel relation. Others of these rays, as the 1104 rays 18, will passdirectly from the filament to the reflector 16 and be reflected inconverging relation to a `iooint lttand thence inl diverging relation asshown. None of the rays Jfrom the ilament will nass directly forwardsbut the opaque kmirror coating will e not appear to cast a shadowbecause the rays 18 meeting at the point 19 will greatly reduce andpractically destroy all shadow effeet. Finally, by proper proportioningthe mirror, certain rays 20 will nass from the '10 lament l2 withoutstriking the reflector ofv the lamp in dii/erging relation and thusilluminate the sides of the roads. lt is, of course., to be understoodthat the :filament and mirror are in proper relation to each 15 other toaccomplish this result. l

By the use of this arrangement it is found that a headlight gives morelight -with the same voltage than with any other lam of correspondingncandle power, the 2U nel of blindness is reduced to a greater degreethan with any other bulb of smooth clear glass lens and it can be usedin the headlight without producing any blinding ehects, and no dark spotor shadow is cast. 25 yllhere has thus been provided a simple and ecientdevice of the kind described and for the purpose sioecied.

intranet I ,if

Having thus described the invention, what is claimed as newe is:

The combination with a headlight having a housing and a main parabolicreflector mounted therein and facing the forward end of the housing andterminating forwardly closely adjacent said end; of a lamp soclretprojecting through the rear end of the relec- 3 tor in the axis thereof.of an incandescent lamp bulb mounted in said socket and han ing itsfilament close to but in front of the focus of the reflector, said bulbbeing coated on its forward end with a reecting surface and a protectingcoating' on said sur face, whereby rays of light from the lame? lamentdirected on the parabolic retlectoh issue in a converging beam, Whilerays old light directed against the reflecting surface 4 on the bulb areredected to the parabolic reflector and redirected by the latter in aparallel beam of light forward of the headlight housing.

lin testimony whereof we afiix our signatures.

WILLIAM WUDRUFF RBERES. LYNN T. EGBERTS.

